The present invention concerns a chair control having an adjustable energy mechanism for supporting the back of a chair during recline.
A synchrotilt chair is described in U.S. Pat. Nos. 5,050,931; 5,567,012; 4,744,603; and 4,776,633 (to Knoblock et al.) having a base assembly with a control, a reclineable back pivoted to the control, and a seat operably mounted to the back and control for synchronous motion as the back is reclined. This prior art chair incorporates a semi-rigid flexible shell that, in combination with the chair support structure, provides a highly controlled postural support during the body movements associated with tasks/work (e.g., when the back is in an upright position) and during the body movements associated with recline/relaxation (e.g., when the chair is in a reclined position). This prior art chair moves a seated user""s upper body away from the user""s work surface as the user reclines, thus providing the user with more area to stretch. However, we have discovered that often users want to remain close to their work surface and want to continue to work at the work surface, even while reclining and relaxing their body and while having continued postural support. In order to do this in the synchrotilt chair of U.S. Pat. No. 5,050,931, users must scoot their chair forwardly after they recline so that they can still easily reach their work surface. They must also push away when they move back to an upright position to avoid being pushed against their work surface. xe2x80x9cScootingxe2x80x9d back and forth once or twice is perhaps not a serious problem, but often users, such as office workers using computers, are constantly moving between upright and reclined positions, such that the process of repeatedly scooting back and forth becomes annoying and disconcerting. In fact, moving around and not staying in a single static position is important to good back health in workers whose jobs require a lot of sitting.
Another disadvantage of moving a seated user""s upper body significantly rearwardly upon recline is that the user""s overall center of gravity moves rearward. By providing a more constant center of gravity, it is possible to design a reclineable chair having greater recline or height adjustment without sacrificing the overall stability of the chair. Also, reclineable chairs that move a seated user""s upper body significantly rearwardly have a relatively large footprint, such that these chairs may bump into furniture or a wall when used in small offices or in a compact work area. Still another disadvantage is that large springs are required in these existing reclineable chairs for back support, which springs are difficult to adjust due to the forces generated by the springs. However, the tension of these springs preferably should be adjustable so that heavier and lighter weight users can adjust the chair to provide a proper amount of support.
Concurrently, seated users want to be able to easily adjust the spring tension for providing support to the back during, recline. Not only do heavier/larger people need greater/firmer back support than lighter/smaller people, but the amount of support required changes at a greater rate during recline. Specifically, lighter/smaller people need a lesser initial level of support as they begin to recline and need a moderately increased level of support as they continue to recline; while heavier/larger people need a significantly higher minimum initial level of support as they begin to recline and need a significantly increased level of support as they continue to recline. Restated, it is desirable to provide a chair that is easily adjustable in its initial level of support to the back during initial recline and that automatically also adjusts the rate of increase in support during recline. Further, it is desirable to provide a mechanism to allow such an easy adjustment (1) while seated; (2) by a relatively weaker person; (3) using easily manipulatable adjustment controls; and (4) while doing so with a control that is not easily damaged by a relatively strong person who may xe2x80x9covertorquexe2x80x9d the control. Further, a compact spring arrangement is desired to provide optimal appearance and to minimize material cost and part size.
Manufacturers are becoming increasingly aware that adequate lumbar support is very important to prevent lower back discomfort and distress in workers who are seated for long periods. A problem is that the spinal shape and body shape of workers vary tremendously, such that it is not possible to satisfy all workers with the same shape. Further, the desired level of firmness or force of support in the lumbar area is different for each person and may vary as a seated user performs different tasks and/or reclines in the chair and/or becomes fatigued. In fact, a static lumbar support is undesirable. Instead, it is desirable to provide different lumbar shapes and levels of support over a work day. Accordingly, an adjustable lumbar system is desired that is constructed to vary the shape and force of lumbar support. At the same time, the adjustable lumbar system must be simple and easy to operate, easily reached while seated, mechanically non-complex and low cost, arid aesthetically/visually pleasing. Preferably, adjustment of the shape and/or force in the lumbar area should not result in wrinkles in the fabric of the chair, nor unacceptable loose/saggy patches in the fabric.
Modem customers and chair purchasers demand a wide variety of chair options and features, and a number of options and features are often designed into chair seats. However, improvement in seats is desired so that a seated user""s weight is adequately supported on the chair seat, but simultaneously so that the thigh area of a seated user is comfortably, adjustably supported in a maimer that adequately allows for major differences in the shape and size of a seated user""s buttocks and thighs. Additionally, it is important that such options and features be incorporated into the chair construction in a way that minimizes the number of parts and maximizes the use of common parts among different options, maximizes efficiencies of manufacturing and assembling, maximizes ease of adjustment and the logicalness of adjustment control positioning, and yet that results in a visually pleasing design.
Accordingly, a chair construction solving the aforementioned problems is desired.
In one aspect of the present invention, a back construction comprises a back frame member and a back having a forwardly-protruding lumbar support section that is characteristically flexible and bendable and configured to engage and posturally support a seated user. The back can be flexed to a plurality of different convex shapes. The top and bottom connections pivotally connected to the back to the back frame at locations above and below the lumbar support section. An adjustable force-generating mechanism is operably attached to the back. The force-generating mechanism is constructed to provide an adjustable biasing force that adjustably biases the lumbar support section forwardly for optimal lumbar support. The force-generating mechanism characteristically provides the biasing force without forcing a shape change in the back.
In another aspect of the present invention, a back shell posturally supports a seated user, comprising a resiliently flexible polymeric including a lower area disposed generally in a pelvic area. A central area is disposed above said lower area and generally in a lumbar area, and an upper area is disposed above said central area and generally in a thoracic area.
Another aspect of the present invention includes a cushion on a forward face of the back shell. A vertically adjustable lumbar support is located in front of the back shell. The lumbar support is movably supported on the back support and configured to change a shape of the sheet in the lumbar area as the lumbar support is vertically moved.
Yet another aspect of the present invention includes a compliant back comprising a flexible shell that has at least one top and at least one bottom connection vertically spaced from the at least one top connection. The bottom connections are in front of a bottom of the shell so that the bottom connections define an axis that is adapted to be generally aligned with a seated adult user""s hip bone when the seated user""s torso is against the shell. The shell has a stiff thoracic section, a stiff pelvic section, and a lumbar section. The lumbar section characteristically is noticeably flexible in a horizontal forward direction, such that the shell can be easily flexed to provide different shapes for optimal lumbar support. The lumbar section is substantially incompressible in directions toward the thoracic and pelvic sections so that the lumbar section causes the thoracic and pelvic sections to pivot along predetermined paths about the top and bottom connections when the lumbar section is flexed. The compliant back undergoes controlled flexure between the top and bottom connections upon flexure of the lumbar section caused by flexure of a seated user""s back.
Another aspect of the present invention includes a seating unit comprising a back frame. A back is operably attached to the back frame at a top connection and operably attached to the back frame at bottom connections. The compliant back includes a stiff thoracic portion and a stiff pelvic portion connected by a flexible lumbar portion. The bottom connections are forward of the pelvic portion and the top and bottom connections. The thoracic, pelvic, and lumbar portions are constructed so that when a seated user flexes their lower back rearwardly, the pelvic portion of the back moves pivotally downwardly and rearwardly. The lumbar portion of the back flexibly moves generally rearwardly to form a more planar arrangement with the pelvic portion. The thoracic portion of the back pivots about the top connection, whereby the compliant back, in combination with the back frame and base assembly, is adapted to provide postural support for a seated user""s back that is very comfortable and yet posturally supports significant flexing and moving of the seated user""s torso and spine.
These and other features, advantages, and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims and appended drawings.